Researches on an organic thin-film light-emitting device in which electrons injected from a cathode and holes injected from an anode emit light when they are recombined in an organic fluorescent body held by both electrodes have been actively conducted in recent years. This light-emitting device is characteristic for high luminance light emission in the form of a thin type and under a low driving voltage, and multicolor light emission due to selection of a fluorescent material, and has been paid attention.
Such researches have undergone many studies for practical use since C. W. Tang et al. of Kodak Co., Ltd. showed that an organic thin-film device emits light at high luminance, and organic thin-film light-emitting devices have steadily come into practical use as they have been employed in main displays of mobile phones, and the like. However, there are still many technical problems and, especially, attainment of both increased efficiency and prolonged life of a device is one of the major problems.
For the organic thin-film light-emitting device, it is necessary to satisfy an improvement in luminous efficiency, a reduction in driving voltage and an improvement in durability. Particularly, realization of both luminous efficiency and durable life is a major problem. For example, materials having a fluoranthene skeleton and a nitrogen-containing heterocyclic ring have been developed for improving luminous efficiency and durable life (see, for example, Patent Documents 1 to 5)